Denon DR-M4

[derek92994]

Important note: I don't have any intentions to piss off the fun of this deck, but you must have in mind this is just middle of the road technology from 30 years back.

It's the fun that counts, nothing more and nothing less.

Well in my world its very high end to me, and what I could afford at this time. The Early 80's decks are my favorites. It has some advantages over my JVC TD-V661. Characteristic of sound is very nice on the Denon, something the JVC does not have. This Denon and my JVC are my top decks and is as good as I'm going to get on my budget. I'm still happy with the JVC and the idea of purchasing the Denon was for quartz lock and that Denon sound in a dual capstan machine.

I have not finished with it yet and still have other ideas on how to fix the problem, cheaply too.

The cassette shells are not the problem. They are high quality and work fine in every other machine. The Denon just needs more adjustments made.

 

[derek92994]

Adjusted take up torque but could not get rid of flutter, is more noticeable at the start of the tape too.

 

[derek92994]

I have installed it in the cabinet as a playback deck, the JVC is still on recording duties.

 

[derek92994]

Been thinking about this deck again. Ruled out the take up torque issue, as even with reduced torque the flutter is still there. Surely the direct drive capstan motor cant be weak, as its hard to stop/slow down, and quartz lock is working as indicated by an led inside being off and then switching on if the speed is adjusted away from the correct tape speed.

Its almost as if the tape is chugging through the take up capstan as if it were being dragged by the take up reel or the pinch roller is losing enough grip for this to occur. But no tape skewing is happening so its not a dead giveaway as to what is wrong. Pinch roller replacement may be worth a try as the problem could go as far as a bad bearing, but to my naked eye it looks perfectly fine and has excellent grip with no cracks, it also turns freely with no resistance. I have never experienced a pinch roller bearing going bad before, only the rubber itself. Could the take up reel motor be 'chugging' like tiny pulsations in the torque or speed that I can't feel by touching the pulley and/or reels, I know that when idlers get old they slip and sometimes vibrate causing wow/flutter regardless of how new the pinch roller is, but this one is not slipping as its new and I have tested it. Capacitors or other circuit board parts could be failing, after all the machine is 30 years old, the possibilities are endless, you can see my frustration here.

Time will tell, much later down the track I MAY just get some parts for it. I really do like the deck and its sound, just this darn mechanical/electrical speed enigma that's bothering me.

I did keep 1 recording made in the deck, and that is a Black Sabbath Mix tape done on a Maxell XLII Chrome, it sounds outstanding and you can't hear the flutter as there are not many high notes. I've had that tape in my car for over a week now and it never gets old, always worth a listen.

Time for some rest.

 

[laatsch55]

You only notice the wow and flutter at high frequencies?

 

[derek92994]

You only notice the wow and flutter at high frequencies?

its the tiniest bit of flutter during high notes, e.g violin, some guitar, flute etc. Its in the pinch rollers, has to be, but of course I'm not sure. None of my other decks do it and its purely mechanical. If I can make it go away by stopping the take up reel it points to mechanical problem, something is inconsistent either roller or take up reel motor, the slightest pulse causing it. Or could be electronics causing the pulse/variation.

 

[laatsch55]

is it a 220 volt machine?

 

[Skywavebe]

When you talk about wow and flutter on a tape that you notice what value is it that you are measuring? The frequency of the wow and flutter might be related to a mechanical part that is rotating at that same rate. Do you have a Torque cassette? Back tension sometimes is a problem to some machines. Make sure not to confuse level variation to that of flutter.
As far as head wear goes, if a head is worn out he metal tape will give exactly the same bad response as any other tape. If you have good results with a metal tape then the other tapes are not biased right or they are being saturated by wrong recording techniques. Keep in mind a lot of LED or other electronics meters are Peak and they are already at +3 when indicating 0dB.

 

[derek92994]

is it a 220 volt machine?

No its a 240 volt model.

 

[derek92994]

When you talk about wow and flutter on a tape that you notice what value is it that you are measuring? The frequency of the wow and flutter might be related to a mechanical part that is rotating at that same rate. Do you have a Torque cassette? Back tension sometimes is a problem to some machines. Make sure not to confuse level variation to that of flutter.
As far as head wear goes, if a head is worn out he metal tape will give exactly the same bad response as any other tape. If you have good results with a metal tape then the other tapes are not biased right or they are being saturated by wrong recording techniques. Keep in mind a lot of LED or other electronics meters are Peak and they are already at +3 when indicating 0dB.

Thanks for your reply Sam.

I can hear it with my bare ears clear as day with a 3khz test cassette, its very slight but its there and comes out through playback/record. Or when there are sustained high notes (e.g. violin, guitar) during music.

I don't have a torque cassette unfortunately. But can honestly say that reducing the take up torque (by lowering the voltage to the motor using a potentiometer) didn't fix the problem. I have no way of measuring back tension, but there is back tension there as I have checked this by rotating the supply reel manually whilst engaged in play mode without a cassette. I don't know if it is the correct amount of back tension though.

I solved the issue of recording/playback fidelity by adjusting the internal bias pot accordingly (edit: only had to make 1 adjustment), so I just need to get this flutter problem sorted. I will record a minute of two of the test tape being played back by this deck and upload it to a dropbox account for you and others to download and have a listen. I'll also playback a musical passage with sustained high notes and record that as well.

But for now, I've just woken up so its time for a coffee and a smoke.

How is your Guard cat? I remember him well =))

 

[derek92994]

Denon DR-M4 sample files (wav format about 20 meg each)

3 Khz Test: https://www.dropbox.com/s/xpzuf9fdos7u1ys/Denon DR-M4 3Khz Test.wav?dl=0

Recording Sample 1: Sony Metal XR60 - Dolby C, recorded by JVC dual capstan deck working well, sourced from vinyl (click/pop filtered) https://www.dropbox.com/s/031wccsywikheca/Denon DR-M4 Sample 1.wav?dl=0

Recording Sample 2: Sony Metal XR60 - Dolby C, recorded by JVC dual capstan deck working well, sourced from vinyl (click/pop filtered) https://www.dropbox.com/s/fkh2k9p8kiey5xr/Denon DR-M4 Sample 2.wav?dl=0

 

[laatsch55]

Good luck Grasshopper...

 

[derek92994]

Good luck Grasshopper...

Morning Lee! and thank you.

Hey its not all bad, at least its an 'ok' playback deck for now, just a slight flutter. Playing rock through it is no issue at all really. But I love the way it records so reaching out to get help with this flutter issue via sound samples for an accurate description of the problem.

 

[laatsch55]

Amen Bud. minus 12 this AM. Gotta go kck out some crews, then Ill be back.,.27 belowat Tim's house....fuel's gellingup.....gonna be a wonderful day...

 

[derek92994]

Amen Bud. minus 12 this AM. Gotta go kck out some crews, then Ill be back.,.27 belowat Tim's house....fuel's gellingup.....gonna be a wonderful day...

You'll tackle it with ease. Extreme cold weather sounds like a bitch indeed, we don't get it here but we do have what we define as 'cold' when it gets below 50F. Do you have to have a 'heater' on your car before cold starting etc? I'm curious about fuel 'gelling up', will hear from you when you're done bud.

 

[laatsch55]

Oh...we have block heaters on all our vehicles. Jani even has one on her gas Ranger. #2 diesel will start to "gel" around minus 25. We are usually running #1by now.

 

[derek92994]

Oh...we have block heaters on all our vehicles. Jani even has one on her gas Ranger. #2 diesel will start to "gel" around minus 25. We are usually running #1by now.

Ahh, so if it gels I assume it can't pump through the fuel line or into the injectors. Diesels can be tricky too when fuel supply is cut from what I remember and need to be 'primed', however in this day and age I would not be surprised that they have technology to overcome that.

My car's a bitch on winter mornings, takes a couple of cranks to start it then idles up and down repeatedly almost stalling each time, then bunny hops up the street for a bit. 2 minutes later she runs good. Its manageable.

 

[derek92994]

Nearly midnight here, 86F and 60% humidity upstairs, 75F and 50% humidity down stairs with a/c on.

 

[Skywavebe]

OK, The Guard cat Mink was PTS back on 3/23 as he was failing quickly in the last two days of his life. At the end he was having trouble breathing and when we got him into the Emergency Vet they gave him oxygen before we said goodbye. He was well loved and we took him in off the driveway so we have no idea how old he was. You know you are old when you dead animals outnumber the ones still alive that are also getting older.


The wow and flutter can be caused by bad bearings for the flywheels and or lack of lubrication of them. I have had no direct experience with the deck you have but I can say that in the Teac line that use dual capstan even with a regular garbage type servo motor (V970X) I have seen wow and flutter at .035%wrms JIS. This you should not be able to hear. In vact they say you can only hear wow and flutter when it is in the .3% or around there. That may mean music not tones. Tones are the things you will hear even sooner and a beginning Technician has to learn that man's technology in the analog cassette is not that good the all wow and flutter is eliminated. The best examples of engineering is present in cassette decks. Many lower grade cassette deck are rated at .1 or .12% wow and flutter with those fine dual cassette decks some of them at .25% when new.
If the belt has not been changed that might be a thing to consider and get one from Marrs not just anywhere. Some people thing a belt is a belt but in these case they are sometimes very particular about the size and thickness and width that is on the deck. Just because a belt is in one piece does not mean it is working well. In the Teac Reel repairs, I get people sending me E bay belted units that have trouble. I put a Marrs belt on and the trouble goes away. This is on the dual capstan X series- this is a larger mechanism but will have the same types of problems.

Back tension- there are models that adjust back tension with a arm that pushes up against the tape and through a spring or string, this can get out of correct condition. This would be observed on a MTT160 torque cassette. I have found that in this kind of design the tuner cord they use gets dirty and needs cleaning. Of course you need to take it off the supply reel table and then adjust it when you put it back. I have to study your units manual to see how it is done but on better units like the Tascam 122 Mk II the back tension is made through a magnetic brake cylinder on the supply reel and is adjusted with a pot. You take up motor can be adjusted with a resistor or a resistor through a power transistor to get lower TU torque but you have conflicting results- stopping the TU gave you better flutter while regulating the reel motor did not. Another thing you have not investigated in might be two things.
1) Have you oiled the reel tables shafts. If you access these from the front usually and you manually take the brake off can they free spin? If not they may be binding.
2) The second idea is if there is a motion sensing wheel or belt that goes off to the rotation sensor. These too can present a frictional component or the belt can be too tight. That is why you want to take note as to the frequency of the wow. The flutter is usually bearings and belt or a higher speed turning item. Some times direct drive motor have a thrust plate that is not greased or the end play is adjusted out by some amateur. There is suppose to be play in all motors and flywheels.

 

[orange]

Well, dang, Sam it still sucks bad losing your buddy.